Have you created a template that selects every row as a detail row (which would be the right thing to do) or are the debits set up as append traps?
If they are append traps you will get the repetition for each detail row.
If the debits are detail then check the field properties in the table window. The exact terminology will depend on the version of Monarch you are using but there is an option under the 'General' tab to fill empty cells with the previous value from that cell or to leave them blank. It sounds like this may be set to 'fill' and you nedd 'blank'.
In the summary the idea works the other way around and normnally you would probably want to show all the keys ion the summary definition for clarity, but sometimes for output to a 'report style' it is easier to read with duplicated or repeated values suppressed from the disply, although they will still exist in the summary calcualtion tables.
I hope this is somewhere close to helping you.
If I have completely misunderstood I apologise - tell me where I go wrong and I will think about it some more ...